Slump indicator for concrete



1963 c. c. STRATTON 3,403,546

SLUMP INDICATOR FOR CONCRETE Filed Aug. 18, 1965 INVENTOR. WHA NN 4 M6MAN/ 5A L A/brneys fbr fi llirab/ by g;

United States Patent 3,403,546 SLUMP INDICATOR FOR CONCRETE Cleo C.Stratton, 1732 Mallory St., San Bernardino, Calif. 92405 Filed Aug. 18,1965, Ser. No. 480,658 1 Claim. (Cl. 73-54) ABSTRACT OF THE DISCLOSURE Aslump indicator for concrete while being mixed in a rotatable mixingbarrel driven from a power source by a power transmitting chain trainedover a drive sprocket and driven sprocket at the barrel, wherein asingle roller is spring urged against the tensioned side of the chain ata point between the sprockets to forcibly deflect the chain from astraight line axis and provide a member movably responsive to variationsin the load torque due to variations in the liquid content of the mix,this member being connected to a resistor for varying the energizationof an ohmmeter calibrated in terms of slump. In mobile mixers, thismeter is mounted in the vehicle cab, and additional resistors areselectively added and removed from the energizing circuit to compensatefor variations in the quantity of the mix being worked in the mixingbarrel.

The present invention relates generally to means for determiningcharacteristics of concrete mixtures, and is more particularly concernedwith means for obtaining accurate and continuous indications of thecharacteristic commonly referred to as slump.

In the mixing of concrete, the liquid content or amount of water thereinis a very important consideration. For example, the amount of water hasa material effect upon the strength of the concrete, when it has curedor dried. Smaller amounts of liquids produce greater strength.Therefore, in those situations where strength is the prime factor, theamount of water is therefore held to a minimum. If strength is not aconsideration, then the use of more water permits easier pouring andfinishing of the concrete.

The above considerations are of primary importance, particularly toproducers of ready-mix or transit-mix concrete, these producers beingconstantly called upon to deliver mixes which may have varying amountsof water. For such mixers, the conventional method of determining theslump is very time consuming and unreliable. In the usual method theslump is determined by means of a slump cone which is approximately 12"high and may vary somewhat as to size. A sample of the mix is placed inthe cone with the cone apex uppermost, and after agitating the cone itis then lifted off and the number of inches which the top of theconcrete cone settles is noted and taken as the slump in inches. Forexample, if the top settles 5", it would be called a 5" slump. Thisprocedure manifestly is very time consuming and may indeed be a verycritical factor in the delivery of concrete which is being mixed duringtransit. In case of delays due to unforeseen hazards, breakdowns or thelike additional tests become necessary, since the mix will becomestiffer as its time in the mixer ice increases, due to the rapidevaporation of the water caused by the heat that is generated from thechemical reaction of the cement and water.

Having the foregoing in mind and the inherent disadvantages of thepresent method utilized to determine slump, it is one object of thepresent invention to provide a unique slump indicator which can be usedfor concrete mixers, and particularly for mobile mixers having powerdriven barrels, and which will continuously provide an indication of theslump characteristic of the concrete mix.

Another object is to provide apparatus which is susceptible of use intransit or mobile mixers, and which embodies a slump indicatorpositioned in the operators cab so that it can be read at any time toremotely indicate the slump characteristic of the material which isbeing mixed in the barrel of the mixer.

It is also an object to provide remote slump indicator means which willbe accurate and continually indicate the slump of a concrete mix whilethe mixing operation is being carried out at a stationary plant, orwhile in transit in a mobile unit, and which may be readily variablyadjusted to compensate for different quantities or amounts of mix.

In its broad concept, the present invention comprises means which areresponsive to variations of load-torque of the mixer barrel, due toeither (a) variations in the liquid content of the mix, or (b) a changein the quantity or amount of the mix being worked or carried, e.g. onecubic yard, two cubic yards, etc. The load-torque responsive means isused to vary a component such as a resistor in the energizing circuit ofan electro-magnetic meter, such as an ohmmeter which is calibrated interms of slump. Additional compensating resistors are provided forselectively changing the energizing circuit so that the 'meter readingswill apply to whatever quantity or amount of the concrete material thatis being mixed.

Further objects of the invention will be brought out in the followingpart of the specification, wherein detailed description is for thepurpose of fully disclosing the invention without placing limitationsthereon.

Referring to the accompanying drawings, which are for illustrativepurposes only:

FIG. 1 is an elevational view of a ready-mix or transitmix vehicle ofthe type utilizing a slump indicator according to the present invention;

FIG. 2 is a view diagrammatically illustrating the torque-loadresponsive sensing mechanism, and further showing its schematiccircuitry interconnection with the remote indicating instrumentalitiesmounted in the cab of the mobile mixer;

FIG. 3 is an enlarged face view of the slump indicating meter; and

FIG. 4 is a fragmentary view diagrammatically illustrating a sensingmechanism utilizing a mechanically actuated slump indicator.

Referring now generally to the drawings, for illustrative purposes,there is shown in FIG. 1 a mobile concrete mixer 10 which isrepresentative of the type of equipment upon which the present inventionhas been installed to indicate slump while in transit.

The mobile mixer is of conventional construction and includes a Wheeledframe structure 11 having an operators cab 12 at its forward end, andrearwardly of the cab mounting a rotatable mixing drum or barrel 13which is supported on end bearing structures 14 and 15 in an inclinedposition with its charging end elevated at the rear end of the vehicle.The charging end is provided with a conventional hopper 16 and isfurther provided with the necessary attachments for unloading the cementat point of destination.

Mobile concrete mixers of this type are constructed with various typesof power transmitting means for rotating the mixing drum or a barrelduring transit. One conventional arrangement embodies a power take-offat the front of the mobile unit in which an engine drive pulley isconnected through a plurality of V-belts with a driven pulley carried bya power transmitting shaft to the rear end of the mobile unit where thepower delivery shaft 17 carries a drive sprocket 18 which is connectedthrough a driving chain 19 with a large annular driven sprocket 20surrounding the charging end of the mixing barrel.

Since the power required to drive the mixing barrel will be directlyproportional to the water content of the mix, and hence provide ameasure of the slump characteristic, provision is made to sense thevariations of loadtorque required to actuate the barrel. In other words,a torque sensing device is utilized between the engine delivery pointand the power delivery point at the barrel. Such devices may constitutea torsion bar which will react to variations of the barrel load. In itsbroad concept, the invention envisions the use of any torque responsivedevice which can be utilized to provide a sensing unit. For illustrativepurposes, however, a simple arrangement will hereinafter be describedwhich may be associated either with the V-belt power take-off at thefront end of the mobile unit, or with the chain drive at the rear end ofthe mobile unit. A device associated with the latter will be described.

As shown in FIG. 2, a load-torque responsive unit A is mounted at therear end of the mobile unit and is connected through conductors 21 and22 with a remote indicating unit B which may be mounted in the cab ofthe mobile unit where it may be readily observed by the operator.

As shown in FIG. 2, the load-torque responsive unit includes a pivotedarm 23 that carries a rotatable member 24 such as a pulley or a gearwhich is urged against the tension side of the chain 19 by means of asuitable spring 25 of predetermined strength so as to deflect the chainin the portion between the drive sprocket 18 and driven sprocket 20laterally from its straight line position. This spring should be ofsufiicient strength to deflect the chain out of line the greatest amountwhen the barrel is empty, that is, when there is no concrete mixtherein. As the sand, rock, raw cement, water and other constituents ofthe mix are placed in the barrel, the power required to rotate thebarrel varies in direct ratio to the amount of water in the mix.Variations of the power required will be reflected by pivotal movementof the arm 23. Thus, as the load increases the chain will becomeincreasingly stressed and swing the arm 23 against the opposing force ofspring 25. This movement of the arm 23 is sensed by a variable resistor26 having a slide contact 27 which is connected to an arm 28 extendingin a direction opposite the arm 23. As thus arranged, as the drivingpower increases, the effective resistance of the variable resistor 26will increase.

By means of the conductors 21 and 22, the load-torque responsive unit Ais remotely connected with the indicating unit B, and a circuit isestablished through the resistor 26 so that it becomes a part of anenergizing circuit by means of which a slump indicating meter 29 isconnected with a battery source 30. One side of the battery 30 isconnected through a conductor 31 and zero adjusting resistor 32 to oneside of the meter 29, while the other side of the battery 30 connectsthrough conductor 21, resistor 2 4 1 26, conductor 22, switch 33,conductor 34, and button switch 35 to the other side of the meter.

The switch 33 is of the single-pole double-throw type having a movableelement 36 which can be selectively engaged with switch contacts 37a and37b. When the movable element of the switch is engaged with the contact37a, the variable resistor 26 is connected into the energizing circuit.Upon connecting the movable element with contact 37b connection is madewith a common con ductor 38 of a resistor network containing a pluralityof individually adjustable resistors 39 for connection in each case by aswitch 40 so as to be placed in the energizing circuit of the meter 29in series relation with the variable resistor 26.

Operation of the remote slump indicator as described above will now beexplained. In order to calibrate the system, the meter 29, which is aconventional ohmmeter, is initially set at its zero resistance positionat the right end of the scale by means of the zero adjusting resistor32. This adjustment is made when there is no charge in the barrel. Thus,only varying power will be shown on the meter. The resistor 26 is chosenof such value that within its range of adjustment it will indicate onthe meter the proper slump reading depending upon the liquid content ofthe mix. The resistor 26 has a value which would correspond with aparticular number of cubic yards which will be mixed in the barrel. Forexample, the resistor 26 would be used for a charge of nine cubic yards.

It will be appreciated that as the amount of charge is reduced, it willtake less power to turn the barrel. As a result, the driving chain 19will be less tensioned so that the action of the spring 25 will permitmovement of the arm 28 in a direction to decrease the effectiveresistance of the resistor 26 with respect to the energizing circuit ofthe meter 29. In order to compensate for this change of load whenworking a smaller charge, the proper resistor 39 is inserted into theenergizing circuit in series with resistor 26. Assume for example thatthe charge being worked is eight cubic yards rather than nine cubicyards. In this case, the resistor 39 as indicated at 8Y would beinserted by closing the switch 40, and moving the element 36 intoengagement with contact 37b. The resistor 39 is properly calibrated forthe eight cubic yard charge. For lesser charges the other resistors ofthe network will be inserted.

As shown in FIG. 3, the slump in inches is indicated on the meter scale41 by numerals in this case which read from zero to nine in increasingopposite direction than that in which the pointer 42 is moved toindicate increasing changes in the resistance of the energizing circuitof the meter. The other compensating resistors for different amounts ofcharge are designated by the indicia 1Y, and 5Y to 9Y inclusive.

While the remote indicating unit arrangement provides for a mostconvenient check by the operator as to the slump of the mix, analternative arrangement is possible wherein mechanical indication ofslump may be provided in connection with the load-torque responsive unitA. Referring to FIG. 4, direct indication may be obtained by providing apointer 43 on the arm 23, this pointer being arranged to traverse ascale bearing member 44 having graduations thereon indicative of theslump for a given number of cubic yards in the mix.

From the foregoing description, it is clearly evident that the inventiondescribed provides an accurate and efficient means for indicating theslump of the mix in a concrete mixing barrel or drum, and that thedelineated objects will be effectively accomplished.

Various modifications may suggest themselves to those skilled in the artwithout departing from the spirit of my invention, and, hence, I do notwish to be restricted to the specific form shown or uses mentioned,except to the extent indicated in the appended claim.

I claim:

1. Slump indicating mechanism for a concrete mixer push having arotatable mixing barrel driven from a power source, said mechanismcomprising:

(a) an electro-magnetic meter having an indicating scale calibrated interms of slump and an energizing circuit;

(b) load-torque responsive means including a resistor in said energizingcircuit variable in accordance with changes of the liquid content in themix; and

(c) other resistors for selectively modifying the energizing circuit tocompensate for variations in the quantity of the mix being worked in thebarrel.

References Cited UNITED STATES PATENTS Roesen 73144 Decker 73-144 XRZanzig 73-136 Cook 7388.5 Moseley 346-32 Hilkemeier 73-54 10 DAVIDSCHONBERG, Primary Examiner.

